This invention generally relates to reclosable packaging and methods for manufacturing reclosable packaging. In particular, the invention relates to the manufacture of reclosable packages on a horizontal-form, vertical fill (HFVF) machine.
Reclosable bags are finding ever-growing acceptance as primary packaging, particularly as packaging for foodstuffs such as cereal, fresh vegetables, snacks and the like. Such bags provide the consumer with the ability to readily store, in a closed, if not sealed, package any unused portion of the packaged product even after the package is initially opened. To gain acceptance as a primary package for foodstuffs, it is virtually mandatory that the package exhibit some form of tamper evidence to protect the consumer and maintain the wholesomeness of the contained product. In addition, in many cases it is necessary that food product be hermetically packaged.
Reclosable fastener assemblies are useful for sealing thermoplastic pouches or bags. Such fastener assemblies typically include a plastic zipper and a plastic slider. Typically, the plastic zippers include a pair of interlockable profiled members that fasten together to form a closure. As the slider moves across the profiles, the profiles are opened or closed. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure members, etc. Reclosable bags having slider-operated zippers are generally more desirable to consumers than bags having zippers without sliders because the slider eliminates the need for the consumer to align the interlockable zipper profiles before causing those profiles to engage.
Methods and apparatus for manufacturing reclosable plastic bags on form-fill-seal (FFS) machines are well known in the art. The use of high-speed automated equipment to form, fill and seal a reclosable package is quite common in the industry.
One known type of FFS machine is a horizontal-form, vertical fill (HFVF) machine that places slider-zipper tape proximal to a fold in a web of bag making film, forms receptacles, and then fills the receptacles through an open package bottom at the top of folded web. This machine typically operates as follows. A pull roller of the HFVF machine draws a continuous length of bag making film dispensed from a supply roll in a machine direction. As the bag making film is dispensed in the machine direction, a flattening roller positions the film on a horizontal plane. At the same time, a continuous length of interlocked zipper tape assembly (without sliders) is unwound from a coil and passed through a slider insertion device. Also a chain or series of sliders is unwound from a coil or supplied by a vibratory hopper and fed to the slider insertion device. The slider insertion device inserts sliders onto the zipper tape at regular spaced intervals corresponding to the length of a zipper in each package. The resulting slider-zipper assembly is placed on the bag making film in alignment with the machine direction. The continuous length of zipper tape assembly with sliders inserted thereon is longitudinally positioned on the bag making film in parallel with and offset from a line where the film will be folded. At a first sealing station, one zipper half is permanently sealed to the film by conduction heat sealing. These permanent seals and the mutual engagement of the zipper profiles maintain the alignment of the slider-zipper assembly with the fold line as the film with attached slider-tape assembly is drawn around a folder plow or board. The folder plow folds the film lengthwise along the fold line. Optionally, as the bag making film is fed over the folder plow, a perforator perforates the film below the interlocking zipper profiles to form respective parallel lines of preferential tearing, where a bag header can be torn off of the package. At a second sealing station, the other zipper half is permanently sealed to the bag making film. At the next station, the opposing walls of the bag making film are cross sealed along a zone transverse to the direction of film movement, the seal zone having sufficient width to form respective side seals on successive packages when the seal zone is cut down the middle by a cutter. The cross seals form discrete receptacles that can be filled before or after the cutting station. After filling, the opposing top edges of the folded web (representing the bottom of the packages) are sealed together at another sealing station, forming a bottom seal. If the bags have been filled before the cutting station, the bag making film is then cut along a side seal to separate the filled package from the web of bag making film.
In accordance with variations of the foregoing machine, the slider-zipper tape assembly can be attached proximal to the top edge of the folded web, i.e., opposite the fold, and the package can be filled either by moving the slider to open the zipper (when both zipper halves are sealed to the film) or by separating the slider-zipper tape assembly from an adjacent unsealed wall of the bag making film, filling the receptacle through the resulting gap, and then sealing the unsealed film wall to the slider-zipper tape assembly. Similar methods of manufacture can be used to make zippered bags that do not have sliders for operating the zipper.
There is a need for a method of manufacture and an apparatus for increasing the production capacity of such HFVF machines.